The development and selection of suitable biomaterials for various blood processing assistance system (heart, lung, liver, kidney) requires a method of materials evaluation which accurately predicts long-term in vivo performance. This proposal describes a new biomaterials evaluation system with well-controlled fluid dynamics, which can be used in a physiologic environment with unanticoagulated blood and no prior exposure to blood to foreign surfaces. New measurement techniques include the development of radioactively tagged protein antibodies to specific portions of the fibrinogen molecule and the use of ultrahigh resolution transmission electron microscopy to identify and characterize protein absorption. Both in vivo and in vitro experiments are proposed to evaluate the capability of the device to assess protein surface adsorption and alteration, platelet adhesion and thrombus formation. Specifically, this new device utilizes the everted inflow technique to direct unaltered blood directly to a test section which may be either a right angle wedge (with constant shear stress over the surface) or a rotating disc (with constant mass transfer and variable shear stress). The system permits use of a well-characterized animal subject, simultaneous exposure of control and test materials in parallel and variable exposure times. In vitro studies focused on fibrinogen adsorption, molecular separation and conformational change and subsequent platelet adhesion and reactivity are proposed. These will be accompanied by paracorporeal animal implants to study both short-term reactions and long-term materials behavior, and attempt to identify correlations between them.